A deba is the primary Japanese fish filleting knife. Unlike the western thin, flexible boning knife that people think of when they hear filleting knife, the deba is thick, rigid, inflexible, and sharpened on a single bevel, but it uses these qualities to its advantage. The heel is thicker than the tip, which allows it to easily remove the head of the fish, while the belly and tip help glide along the ribs and spine, allowing for very little waste. It is available in a wide range of sizes, depending on the fish it is used on. A deba used on trout would generally be around 180mm to 240mm.